number of whole seconds since the Unix epoch. For times before
the Unix epoch, this is a negative number. Note that in %s.%q and %s%Q
the decimals are positive, not negative. For example, 0.9 seconds
before the Unix epoch is formatted as -1.1 with %s%Q.

Builds a time value from a parsed input string.
If the input does not include all the information needed to
construct a complete value, any missing parts should be taken
from 1970-01-01 00:00:00 +0000 (which was a Thursday).